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I recently purchased a miniITX based PC to act as the home network router, firewall, mail server, etc. Equipped with a 30Gb 2.5" HDD, this completely fanless machine (from Lex) is a functional workstation and file server, whilst costing only a little more than an appliance router/firewall.

However, the PC is not equipped with a floppy or optical drive, raising the question of how to install an OS on it. A number of options were available:

Boot from a USB CDROM or HDD. Nice idea, but I don't own one, and the PC only supports USB 1.1, which would be rather slow.
Put the HDD in another machine, do the install, and replace it. That would require buying a wiring adapter to put the 2.5" drive in a desktop machine.
Use the IDE connector on the motherboard to attach an optical drive, powered by a separate PSU. I really didn't like the idea of having a separate PSU hooked up to the machine. Who knows how well isolated power and data ground are?
Network boot. Cool :)

I remembered the bizarre wonder I felt when I network booted an old SparcStation2 a few years back. It's really weird seeing a machine doing something useful without a local disk. Don't know why. Anyway, I figured network booting this machine was the way to go. I would then do a network install of the OS to the local drive. Over 100Mbps ethernet, it shouldn't be too slow either.

A few downloads to my existing server were required:

RedHat 9 .iso images.
SYSLINUX tarball (local copy)
tftp-hpa tarball (local copy)

Client PC configuration

The PC was initially configured to network boot. The parameters can be found in the RealTek Boot Agent, which can be configured by pressing Shift-F10 as indicated as each network interface is initialised when the machine boots. The required settings are:

Network Boot Protocol : PXE
Boot Order: Int19H (this tries a network boot first, then uses the BIOS boot order)

At this point, it is wise to note the MAC (hardware) address of the network interface from which the machine will be booting.

DHCP server configuration.

The basic process of PXE network booting is pretty straightforward. The PC broadcasts for a DHCP server. The server responds and provides the address of a tftp server, and the file that should be retrieved from the tftp to act as a boot image.

As I was already running dhcpd on my server, all that was required was some editing of /etc/dhcpd.conf. I added the lines:

allow booting;
allow bootp;

group {
 next-server 192.168.0.254;

 host delirium {
  hardware ethernet 00:40:F4:67:3E:24;
  filename "/tftpboot/pxelinux.0";
 }
}

The address 192.168.0.254 is the IP of the tftp server, which in my case was the same as the dhcp server. The hardware address is that of the client machine (given the hostname 'delirium'). This configuration means that the client machine will attempt to boot from the image /tftpboot/pxelinux.0 loaded from the tftp server at 192.168.0.254.

Restarting dhcpd and rebooting the client resulted in the PXE boot ROM complaining that the tftp server wasn't responding. Fair enough.

tftp server configuration.

Not all tftp servers are born equal, and some just don't work for PXE booting. I would recommend the tftp-hpa server, linked above. Untar, ./configure, make, make install as usual. Then add to your inetd. I added following to /etc/inetd.conf :

tftp   dgram   udp     wait    root    /usr/sbin/tcpd  in.tftpd

Make sure that you allow connections from the client PC through TCP wrappers, or whatever security you have on your inetd.
Restarting inetd and rebooting the client now resulted in a message that the required file (/tftpboot/pxelinux.0) could not be found.

Next, I created a /tftpboot/ directory, and placed in it the pxelinux.0 from the SYSLINUX package. I then copied the files initrd.img and vmlinuz from the /images/pxeboot/ directory of the first RedHat CD to /tftpboot/. I then created a directory /tftpboot/pxelinux.cfg/ and placed in it a file called default which contained the following text:

default linux
prompt 1

label linux
 kernel vmlinuz
 append initrd=initrd.img devfs=nomount

This completed the server configuration. Now when the client was rebooted, it retrieved the pxelinux.0 image, which acts much like lilo and uses the ./pxelinux.cfg/default file to present the boot options - in this case 'linux' which uses the RedHat 9 network install kernel and root disk.

Network installation of RedHat 9.

This was really easy. I installed apache on my server, and copied the contents of the RedHat directories of the RedHat CDs into a directory served by the webserver. I then chose http installation from the options presented after the RedHat installer had been loaded by the client. Follow the instructions onscreen. Exactly like doing a local disk installation.

Making the client boot from its own disk.

As the PC had come configured for PXE booting, I hadn't bothered to play around with the RealTek Boot Agent when I first started the installation. That meant that when I finished the install, and wanted to boot from the local HDD, I just changed the BIOS boot order to HDD, then LAN. This did nothing, and the machine continued to attempt network booting only. Of course, the answer was to press Shift-F10 as the network interfaces initialised, and set:

Boot Order: Int18H

This means that the BIOS controls the boot sequence, and a HDD boot became possible.
Job done.